WASHINGTON — Two U.S. officials say slain Boston bombing suspect Tamerlan Tsarnaev was an ardent reader of jihadist websites and extremist propaganda in the run-up to last week's marathon attacks that killed three people and wounded 180.

Authorities believe neither Tamerlan nor his younger brother Dzhokhar had links to terror groups. But law enforcement officials have concluded based on an early interrogation and other evidence that the two brothers were motivated by an anti-American, radical version of Islam.

On Tuesday, two officials said that Tamerlan frequently looked at extremist propaganda, including Inspire magazine, an English-language online publication aimed at aspiring lone-wolf terrorists.

Both officials spoke on condition of anonymity because they were not authorized to discuss the investigation publicly.